ohsp driver: Does this driver works with usb connections?

[klahm]

Hello,

I bought a balance that supports both RS232 and usb connections. Unfortunately my notebook only supports usb. I did not get the vi (ohsp) to work so I am wondering wether the driver ohsp does support usb ! If not how can I change the VISA setup to connect to the balance via usb ??

Maybe there is a similar driver for another instrument that can be altered  in a way.

Steps I tried: Installation of the latest VISA (4.something); installation of the usb drivers that came with the balace; changing VISA recourse in the ohsp.vi to usb raw and others (the vi complained about broken wires because of data mismatch)

Thanks

Thorsten, University of Technology Berlin, Germany

[jjp377]

Hello,

The driver only supports serial interface, but the help (in Initialize.vi) mentions USB interface kit included on the CD (below)

Notes:

(1)  Either the SCOUT Pro RS232 or USB Interface Kit is required for use with this driver.

(2)  The USB Interface kit includes a CD with the software drivers to create the required virtual port on the computer.
When sending a command from a computer to the balance, the application program sends a command to the virtual port as if it were an RS232 port.  The computer then directs the command from the virtual port to the computers USB connector where the balance is connected.  The Adapter Kit receives the USB signal and reacts to the command.

[Dennis_Knutson]

The first thing to determine is whether the USB is emulating an RS-232 port. If it is, then when you installed the driver and plugged the instrument into the pc, you would see a new serial port in windows device manager and in MAX (Measurment & Automation Explorer). If it does, then the driver should work. If a new serial port does not appear, then check in MAX and device manager if the instrument is using USB TMC. The Test and Measurement Class should also allow you to use the driver with a few small modifications. If the instrument is another class (i.e. HID), then you will have quite a bit of work to do. You will have to create an inf file for the instrument that defines it as a VISA connection and then use the USB RAW functions to read/write to the device after you get some pretty detailed information from the vendor.

If not RS-232 or USB TMC, the simplest thing would be to get a simple USB-RS232 converter. They are inexpensive.

[Albert.Geven]

You probably can use the usb port as a serial port from the software point of view.
Normally the driver emulates a virtual serial port.

good luck

[klahm]

Thanks a lot for the replies.

@jjp377: Thank you for these details. I wondered wether this driver utility (FTDI driver) I found on the CD may corrupt the interaction of ohsp vis with the hardware but you showed there is a  need for this driver. Actually After installing the FTDI driver I have found a new port COM4. In Windows hardware manager I changed this to COM1 because in the FTDI Documentation they said I can do so.

I tried the vi read_measurement.vi but there was a VISA error. I installed VISA 4.3 and used the MAX utility to check the interaction with the hardware and I got the error saying a VISA session could not be opened because the device is busy. (I forgot the exact error message text)

I uninstalled the FTDI driver and used MAX again. Know I see COM3 but I do not know wether the balance uses this port or not. I can open a VISA session but I do not know wether a message like P\n is the right thing to do.

@dennis Kn...: Thanks for your guidelines. I will try to figure out wether "the instrument is using USB TMC" but may be it is faster you tell me how to do it 😉 I 've read the ni documentation about USB TMC and USB raw and I really do not like the idea that it is a USB raw device.

ok, I will try a few things know and hope to ask at least more specific questions. If somebody can post how I can distinguish between usb port and serial port (does COM always mean RS232?) and how I can use the windows device manager to get the information about USB TMC, it would be nice.

Thanks
Thorsten

[klahm]

OK, I reinstalled the driver FTDI and now it works juhuuuuu

Thanks for your replies

[Dennis_Knutson]

The FTDI driver is setting the connection as RS232 (Comx) and you do not need to check if it is TMC.

I don't understand how you can remove the FTDI driver and still see a com port. Did you just remove the inf file or did you remove both the inf and pnf?

I would suggest you start by leaving everything as is after installing the USB driver. See if you get the busy error with that. Usually, it means that you have multiple resources tryinbg to access the same port. For example, windows will not allow you to use Hyperterminal and LabVIEW at the same time on the same port.

[Albert.Geven]

In my laptop com3 is the infrared port